Ladle transfer cars have been utilized in the metals industry for many years. In steelmaking operations, ladle transfer cars are commonly used in basic oxygen furnace shops to transport ladles full of molten steel from the furnace area to the teeming aisle or pouring area. More particularly, in many basic oxygen furnace shops molten steel is poured from the furnace into a ladle that is positioned beneath the furnace upon a ladle transfer car. The transfer car rides along a pair of rails which are mounted along the floor of the furnace shop. The rails extend from beneath the furnace to the pouring area. After the molten metal is emptied from the furnace into the ladle, the transfer car rides along the rails transporting the ladle from beneath the furnace to the pouring area. When the transfer car arrives in the pouring area, the ladle is removed from the transfer car by an overhead crane and the pouring operation is commenced. Upon completion of the pouring operation, the empty ladle is placed back onto the transfer car and the ladle is transported by the transfer car back beneath the furnace.
Determining the weight of the molten metal which is poured from the furnace and contained in the ladle is important to both the quality and overall efficiency of the steelmaking operation. Specifically, the weight of the molten metal must be known in order to ensure that proper alloy additions are made to the ladle. Improper ladle additions can lead to the scrapping or rejection of an entire heat of up to 300 tons of steel. Also, knowing the weight of the molten metal helps to ensure that the proper amount of metal is poured into the individual molds that comprise a drag or series of molds thereby helping to prevent the pouring of the last or trailer mold of a drag to an insufficient height. The pouring of the last mold to an insufficient height often results in the ingot associated with the mold being rejected or scrapped. If the weight of the molten metal is known prior to beginning the pouring operation, and it is determined that there will be insufficient metal left in the ladle to pour the last mold, any molten metal left in the ladle after the pouring of the second to last mold on a drag may merely be poured back into the furnace and recycled thereby avoiding the cost of reheating the metal and other related production expenses.
Various attempts have been made in the prior art to provide ladle transfer cars with weighing systems. Some of these prior art ladle transfer cars have included the use of shear beam load cell pins. These pins connect the car body of the transfer car to the various truck assemblies which support the car body upon the rails. Each of the pins includes strain gauges which generate an electrical signal corresponding to the weight supported by the pins. The pins are electrically connected through a summing box to a weigh instrument which converts the electrical signal transmitted from the pins to a weight.
Unfortunately, prior art ladle transfer cars with weighing systems have been found to produce inaccurate and unreliable weights. This may be due in part to the extraordinarily harsh environment in which the ladle transfer cars must operate. More particularly, molten metal is sometimes spilled on the transfer cars and the cars continually experience shock loading and horizontal loads as a result of the rough handling of the ladles (which can weigh over 300 tons when full) by overhead cranes which lift and set the ladles upon the transfer cars.